The present invention relates to an optical disk device, and particularly to that wherein medium information reading is appropriately performed by detecting removal of a recording medium loaded therein, and an information reading method applied in the optical disk device.
In many optical disk devices, there is provided a means for detecting whether a recording medium is set or not.
In a Japanese utility model application laid open as a Provisional Publication No. 32736/'95, there is disclosed a recording medium detecting means, which is used for easily discriminating whether a CD (Compact Disk) is accommodated or not in each of CD trays provided in a magazine. For the purpose, a detecting pin, which is protruding towards a CD storage space, is provided in each of the CD trays of the magazine. The detecting pin is pushed when a CD is set in the storage space, and turns a mark provided at a visible end of each of the CD trays. A photo-detector provided on a CD-tray elevator, which takes charge of loading a CD tray on a CD player, detects turning of the mark. Information of the mark thus detected is stored in a memory for each of the CD trays to be referred to afterward.
In a Japanese patent application laid open as a Provisional Publication No. 38676/'92, another detecting means is disclosed, wherein an optical reflection detecting element is used in combination with a transparent hole provided in a base of a disk tray. When the disk tray with a disk is set at a loaded position, a detection light radiated from the optical reflection detecting element fixed to a chassis is projected through the transparent hole onto a recording surface of the disk to be reflected thereby. By catching the reflected detection light returning through the transparent hole, the optical reflection detecting element confirms existence of a readable disk. When the disk tray arrives at a certain position in an ejecting process of the disk tray, a reflection piece provided at a back end of the disk tray comes upward of the optical reflection detecting element, and reflects the detection light again, which is catched by the optical reflection detecting element so that the accomplishment of the ejecting process is confirmed.
Further, in many optical disk devices, when setting of a recording medium is detected making use of a recording medium detecting means such as above described, medium information concerning the recording medium itself, such as directory information, header addresses of contents or information concerning defect sectors, is read out and stored in a memory, prior to receiving read/write commands of the contents, so that the information reading/writing of the contents can be performed immediately, when a read/write command is received, referring to the medium information thus prepared in the memory.
However, this pre-reading of the medium information has been conventionally performed only based on whether a readable recording medium is set or not. Hence, every time a disk tray is loaded (after an ejection) on an optical disk device, the pre-reading of the medium information is performed again on the assumption that the recording medium is possible to have been changed, even when the disk tray is re-loaded without changing the recording medium.
This takes unnecessary time to be wasted until information reading/writing of a desired contents begins.